The miniaturization of electronic components, for which a resolution down to the range of less than 1 μm is required, has been achieved substantially by photolithographic techniques. For a further higher resolution, miniaturization is being achieved by the progress of immersion lithography technologies using ArF having a short exposure wavelength as a light source. However, such technologies for forming a pattern with a line width of 32 nm or less have more and more suffered from problems such as line edge roughness depending on the physical properties of a resin to be used. On the other hand, the higher and higher requirements with respect to resolution, wall slope, and aspect ratio (ratio of height to resolution) result in a cost explosion in the case of masks, mask aligners, steppers, and other apparatuses required for photolithographic structuring. Among them, owing to their very high price, modern steppers are a considerable cost factor in microchip production as a whole. Independently, there is an attempt to use short-wave radiation, such as electron beams and X-rays, for achieving a higher resolution. However, this technique still has many problems when adopted to mass production.
Liquid crystal displays each generally employ two or more functional films typically including a light guide, a prism sheet, a deflector plate, and an anti-reflection film for satisfactory viewing angle and high brightness. However, to obtain these functions using films composed of a thermoplastic film, it is necessary that the thermoplastic resin is heated to a temperature around its glass transition temperature Tg, a pattern is transferred thereto, the patterned thermoplastic resin is cooled to room temperature, from which the mold is removed, and these operations cause a problem in throughput. In contrast, a thermal imprinting technique through coating allows curing to be easily performed at lower temperatures and thereby enables a higher throughput. UV-based nanoimprint lithography (UV-NIL) is a technique according to which patterning is performed by applying a liquid photocurable resin to a substrate at room temperature; stamping an optically transparent mold onto the applied resin; and applying an ultraviolet ray (UV) to cure the resin on the substrate to form a pattern. This technique enables pattern transfer at room temperature and is expected typically for (i) a high throughput and (ii) pattern transfer with high resolution or definition. However, if the expensive mold is contaminated with the liquid UV-NIL material during microprocessing, it is very difficult to recycle or reuse the mold, because the liquid UV-NIL material is cured through UV curing into a solid that is insoluble in solvents.
U.S. Pat. No. 5,772,905 discloses a nanoimprinting process as a process for forming a fine convexo-concave pattern on a film. This process applies thermoplastic deformation to a resist using a relief-formed rigid stamp, which resist is applied to the entire surface of a substrate (wafer) and is composed of a thermoplastic resin. This process employs a thermoplastic resin (poly(methyl methacrylate), PMMA) as a hot-stamping resist. However, owing to common thickness variations of about 100 nm over the entire wafer surface, it is not possible to structure a 6-, 8-, or 12-inch wafer in one step with a rigid stamp. Thus, a complicated “step and repeat” method would have to be used, which, however, is unsuitable in consideration of production process, owing to the reheating of already structured neighboring areas.
Japanese Unexamined Patent Application Publication (JP-A) No. 2007-186570 discloses, as a process for forming a fine pattern through UV-based nanoimprinting, a process of using a composition which contains a (meth)acrylate monomer having an alicyclic functional group and shows satisfactory dry etching resistance. This process, however, still suffers from a problem that a cured product of the composition is difficult to be removed from the mold when the mold is contaminated with the composition, because the multifunctional monomer has been three-dimensionally cured.
Japanese Unexamined Patent Application Publication (JP-A) No. 2007-1250 reports another nanoimprinting technique as a process for forming a fine pattern through nanoimprinting, in which a fluorocarbon polymer is used for improved mold releasability. This technique reduces the frequency of mold contamination but still insufficiently, and the problem in removal of the cured product upon mold contamination still remains as a significant problem.
Independently, an imprinting technique using an alkali-developable resist enables mold recycling or reusing. However, though being effective typically for peeling off of the cured article (fine pattern) from the mold, the alkali-developable resist is very difficult to be removed from the fine pattern through dissolution, because a resin constituting the resist is not thoroughly dissolved in an alkali but is suspended therein.